The violence and looting, which began on Saturday in Tottenham, has also spread to Birmingham, Bristol and Liverpool, Sky News reported Tuesday afternoon, with 300 people arrested and 36 charged so far.

More than 1,700 extra police officers were deployed across the capital overnight as violent scenes broke out, it says.

Police in Croydon are investigating a "non-fatal" shooting and all London football clubs have been ordered to call off matches.

In Ealing, gangs of youths started fires in the street and vandalized shops, according to eyewitnesses, Sky News reports.

British Prime Minister David Cameron cut short a vacation in Tuscany, arriving in the early hours of the morning, for crisis meetings, BBC reports.

He will meet Home Secretary Theresa May and Acting Scotland Yard Commissioner Tim Godwin before chairing a meeting of the Cobra emergency planning committee at 09.00 BST.

Asked why the PM had now decided to return from his holiday, after earlier saying he would not, a Downing Street source said: "The situation has become more serious."

Godwin called it another wave of "gratuitous" violence and urged families to help police bring the situation under control.

"I do urge now that parents start contacting their children and asking where their children are," he said.

"There are far too many spectators who are getting in the way of the police operation to tackle criminal thuggery and burglary."

Labour leader Ed Miliband is also returning to London from his break.

Looting and raging fires have plagued the world city with waves of street anarchy, including fresh riots on Monday close to the stadiums built for the 2012 Olympic Games, the Washington Post reported.

TV cameras showed hundreds of youths of all races looting shops, setting businesses ablaze and clashing with police in at least a half-dozen neighborhoods, shocking the world and causing soul searching among many Londoners.

Home Secretary Theresa May has condemned the riots as "sheer criminality," the BBC reported.

The violence began with a riot that initially tore through London's deprived Tottenham neighborhood on Saturday following a police shooting of a young black man, Mark Duggan. It harkened to an earlier era of racial unrest in Tottenham. But the riots have continued to spread since Saturday. And no one believes the current chaos has anything to do with Mark Duggan, the BBC reported.

Rioters have attacked double-decker buses and fire quickly spread down a street side in south London, the Washington Post reported. Most of a block in the southern neighborhood of Croydon raged in flames.

The embattled Metropolitan Police called in reinforcements from police forces outside London to help cope.

The BBC's live coverage reported further violence between police and groups of young people in the neighborhood of Hackney and at least five other neighborhoods. Fires have also broken out in Lewisham, Peckham, Croydon and Clapham Junction.

Shop windows have been smashed and looting has also taken place in Birmingham.

"I have never seen such a disregard for human life. I hope they rot in hell," said Croydon pub landlord Alan McCabe. "The grief they have caused people, the fear they have put in people's hearts, decent people who have done nothing to anyone."

Acting Metropolitan Police Commissioner Tim Godwin has said the force will be publishing photos and CCTV footage of those involved.

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